Pathophysiology Notes: Modules 1, 2, & 3 Module 1

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Pathophysiology Notes: Modules 1, 2, & 3 Module 1 Chapter 2: Homeostasis, Allostasis, and Adaptive Responses to Stressors Homeostasis & Allostasis Homeostasis: ❖ Remaining stable while staying ... the same ❖ A state in which allsystems are in balance ❖ A state of equilibrium ❖ An ideal “set point” despite alterations within the body Allostasis: ❖ Ability to successfully adapt to challenges ❖ Intricate regulatory processes orchestrated by the brain ❖ A dynamic process that maintains or re-establishes homeostasis in light of environmental and lifestyle changes Stress As A Concept ❖ Physical, chemical, or emotional factor resulting in tension of body or mind ❖ Actual physical and mental state that tension produces ❖ Real or perceived threat to homeostasis ❖ Direct consciously or indirect unconsciously sensed threat to the stability of the organism ❖ Physical, chemical, or emotional factor resulting in tension of body or mind ❖ Actual physical and mental state that tension produces ❖ Real or perceived threat to homeostasis ❖ Direct consciously or indirect unconsciously sensed threat to the stability of the organism General Adaptation Syndrome (GAS) (Selye) ❖ Three stages: Alarm,resistance/adaption, and exhaustion ➢ Alarm stage: fight-or-flight response asthe result ofstressfulstimulus ▪ Hypothalamic-pituitary-adrenal (HPA) axis ➢ Resistance/adaptation: activity of the nervous and endocrine systems in returning the body to homeostasis ▪ Allostatic state: activity of varioussystems attempting to restore homeostasis ➢ Exhaustion: point where body can no longer return to homeostasis ▪ Allostatic overload: “cost” of body’s organs and tissues for an excessive or ineffectively regulated allostatic response; effect of “wear and tear” on the body P. 16 Fig. 2-2; P. 15 ❖ Stressors ➢ Agents or conditionsthat can produce stress; endanger homeostasis ▪ May be external or internal • External examples:school, work, life event (wedding) • Internal examples: cancer, child birth/pregnancy ▪ Physical, chemical, biological, social, cultural or psychological • Physical: hand injury • Social:standing in front of a class • Cultural: acceptance/ability to practice ▪ Vary in scope, intensity, and duration ▪ Reactions to stress vary depending upon genetic constitution, gender, past experiences, cultural influences, developmental stage, and age • Past experience: a child afraid of a playground b/c he was previously abused there ▪ Can include both negatively and positively perceived events ➢ Risk Factors: Not stressors, but conditions or situations that increase the likelihood of encountering a stressor; there is some control over our stressors ❖ Neurohormonal Mediators of Stress & Adaption ➢ Catecholamines ▪ Play an integral role in allostasis ▪ Symphathico-adrenalsystem response mediatesthe fight or flight response ▪ Examples: Norepinephrine and epinephrine ➢ Norepinephrine ▪ Constricts blood vessels and raises blood pressure ▪ Reduces gastric secretions ➢ Epinephrine ▪ Enhances myocardial contractibility, increases heart rate, and increases cardiac output ▪ Causes bronchodilation ▪ Increase the release of glucose from the liver (glycogenolysis) and elevates blood glucose levels ➢ Adrenocortical Steroids ▪ Critical to maintenance of homeostasis ▪ May synergize or antagonize effects of catecholamines • Examples: Cortisol and aldosterone ▪ Cortisol • Primary glucocorticoid • Affects protein metabolism • Promotes appetite and food-seeking behaviors • Had anti-inflammatory effects • Too much cortisol over time can lead to pro-inflammatory effects ▪ Aldosterone (secreted by the adrenal cortex) [Show More]

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